Hitherto, in the field of element-sealing for electronic part apparatuses such as transistors and ICs, sealing with resin has become a main current from the viewpoint of productivity, costs and others, and epoxy resin compositions have widely been used. The reason therefor is that epoxy resin is good in balance between various properties such as workability, formability, electric characteristics, moisture resistance, heat resistance, mechanical characteristics, and adhesiveness to inserted parts. In semiconductor devices undergoing bare chip packaging, such as a COB (Chip on Board), a COG (Chip on Glass), and a TCP (Tape Carrier Package), a liquid resin composition for electronic part sealing is widely used as a sealant. In a semiconductor device (of a flip-chip type) wherein semiconductor elements are connected directly to a wiring substrate wherein a ceramic, a glass/epoxy resin, a glass/imide resin, a polyimide film or the like is used as a base by means of bumps, a liquid resin composition for electronic part sealing is used as an underfill material with which a gap between the semiconductor elements and the wiring substrate that are bump-connected is filled. The liquid resin composition for electronic part sealing fulfils an important function in order to protect electronic parts from temperature, humidity, and mechanical external force.
As a hardening agent in a resin composition for electronic part sealing, an acid anhydride based hardening agent has been frequently used so far. The reason therefor is that a liquid material having a low viscosity is easily available and further the hardening performance can also be adjusted with relative ease by selecting a hardening accelerator. However, in the case of using the acid anhydride based hardening agent, there is generated a drawback that the moisture resistance of the hardened product is poor. Thus, from the viewpoint of an improvement in the moisture resistance, underfill materials wherein an amine based hardening agent is used as a hardening agent have been becoming a main current (see, for example, JP-A-2005-350618).
However, the progress of semiconductors is remarkable; according to the flip-chip type, wherein bump-connection is performed, the pitch of bumps becomes narrower and the height of the bumps becomes smaller as the number of the bumps becomes larger. As a result, the gap has been becoming narrower. Moreover, as the integration degree of semiconductor elements becomes higher, the chip size also becomes larger. For any underfill material, a property that the material flows onto a larger area in a narrow gap has been required. As the gap becomes narrower, the number of the bumps increases and the pitch of the bumps also becomes narrower. Thus, the flowing path of the underfill material becomes complicated, and voids are easily generated. Furthermore, an underfill material fills into the gap between a wiring substrate and semiconductor elements, and then a given amount of the material exudes into the vicinity of the semiconductor elements so that fillets are formed. If the shapes of the fillets are uneven, the fillets may be cracked at the time of temperature cycles or at some other time, or the underfill material may be peeled from the wiring board or the semiconductor elements. Such generation of voids or formation of uneven fillets produces a larger effect onto the reliability of semiconductor devices undergoing flip-chip packaging. In particular, about such voids, those skilled in the art have been understanding that it is effective for decreasing the generation of the voids that after an underfill material is filled, the material is quickly hardened.
As described above, about conventional acid anhydride based hardening agents, the adjustment of the hardening performance thereof is relatively easy; however, about amine based hardening agents, the adjustment of the hardening performance is generally difficult. Thus, when the hardening performance is made large, a problem that the adhesiveness lowers is caused.
An object of the invention is to provide a liquid resin composition for electronic part sealing which is good in fluidity in a narrow gap, is free from the generation of voids, and is excellent in fillet-forming performance; and a highly reliable electronic part apparatus provided with an electronic part sealed with this composition so as to give excellent moisture resistance and thermal shock resistance.